1. Field of the Invention
The present invention relates to a liquid-cooling type cathode-ray tube apparatus to be used in a projection type television, and in particular to a liquid-cooling type cathode-ray tube apparatus in which stray light projected onto a screen is shielded.
2. Description of the Related Art
As for the color video projection system for projecting an enlarged image onto a large sized screen as a projection type television apparatus, various configurations have heretofore been proposed. Recently, a collective type projection television apparatus having a screen and a projector incorporated into a single cabinet is widely used. FIG. 1 shows a schematic diagram of such a projection type television apparatus 16, in which within a cabinet 2, a screen 3 is fitted to its upper front face, and on the upper rear face of the cabinet 2, a reflective mirror 4 is disposed in such a position as opposed to the screen 3.
A liquid-cooling type cathode-ray device 5 functioning as a projection tube is disposed so as to be opposed to the face of the reflective mirror 4. As for the projection type television apparatus 16, its size reduction has been attempted. As shown by one-dot chain line, therefore, the cabinet 2 has been lowered in height. As a result, the liquid-cooling type cathode-ray tube apparatus 5 has been disposed at an upper position.
Typically, a projected light 6 projected from the liquid-cooling type cathode-ray tube apparatus 5 is reflected by the reflective mirror 4 and made incident on the screen 3. Thus, a predetermined image is projected onto the screen 3. As a result, it is possible to see the projected picture in front of the screen 3.
The liquid-cooling type cathode-ray tube apparatus 5 used in the projection type television apparatus 16 described above is configured as shown in FIG. 2. In FIG. 2, a cooling liquid 9 for cooling the front face of a face panel 8 of a CRT 1 is contained in a coupler 10. The cooling liquid 9 is disposed between the face panel 8 and a lens 11. Although not illustrated, a pressure regulating valve for controlling the pressure of the cooling liquid 9 and a pressure regulating valve holder are disposed in the coupler 10. Reference numeral 12 denotes a sealing screw for sealing a cooling liquid pouring inlet 30 provided at an upper part of the coupler 10, and for maintaining air-tightness, the sealing screw 12 has a packing. Reference numeral 13 denotes a lens plate for supporting the lens 11. Reference numeral 14 denotes an O ring for maintaining the air tightness.
As shown in FIG. 3 which is an enlarged view of a portion A of FIG. 2, the lens 11 and the coupler 10 are sealed via the O ring 14 so as to be airtight. For the purpose of this sealing in air-tightness, the periphery of the lens plate 13 is pressed and attached to the coupler 10 by means of a screw 15.
According to the projection type television apparatus 16 having the above described configuration, the light emitted from the face panel 3 of the liquid-cooling type cathode-ray tube apparatus 5 housed in the cabinet 2 is emitted in the direction to the reflective mirror 4 via the cooling liquid 9 contained in the coupler 10 and the lens 11. However, the light subjected to diffused reflection in the coupler 10 is emitted as stray light 7 in the direction of a flange (peripheral edge) of the lens 11 as shown in FIG. 3, and irradiates a predetermined region 3a of the screen 3 as shown in FIG. 1. Therefore, the portion irradiated with the stray light becomes bright, resulting in degradation of the picture quality of the television apparatus.